improve performance of avro map reduce jobs

[ey-chih chow]

Our Map/Reduce jobs are all based on avro.  We would like to enhance their 
performance.  The objects collected in our mappers and reducers are mainly of 
the type GenericData.Record.  Currently, most of jobs are CPU, rather than IO, 
bound.  Can anybody suggest ways to improve the performance of the jobs?  
Thanks a lot.
Ey-Chih Chow